The present invention relates to a scroll fluid machine such as a scroll compressor, a scroll vacuum pump, a scroll expander or a scroll blower.
In such a scroll fluid machine, an orbiting scroll is rotatably secured to an eccentric axial portion of a driving shaft via a bearing. On an orbiting end plate of the orbiting scroll, an orbiting wrap engages with a stationary wrap on a stationary end plate of a stationary scroll to form a sealed chamber between the orbiting and stationary wraps. There are provided a plurality of self-rotation preventing devices for preventing the orbiting scroll from rotating on its own axis.
By revolving the ordinary scroll with the eccentric axial portion of the driving shaft, fluid sucked from the outer circumference into the sealed chamber is compressed towards its center or fluid sucked from the center is decompressed towards the outer circumference.
A known scroll compressor is shown in FIG. 5 and will be described below. The present invention can be applied to a scroll expander or other scroll fluid machines as well. In FIG. 5, the left and right sides are deemed as the front and rear respectively.
A stationary scroll 1 in the front or left side of FIG. 5 comprises a circular stationary end plate 8 which has an intake port 2 on the outer circumference and a discharge port 3 at its center. The stationary end plate 8 has a spiral stationary wrap 5 on the rear surface and a plurality of corrugated equal-height cooling fins 10 on the rear surface.
An orbiting scroll 7 is provided behind the stationary scroll 1 and comprises an orbiting end plate 8 which has a spiral orbiting wrap 9 on the front surface which faces the stationary scroll 1, and a plurality of corrugated equal-height cooling fins 10 on the rear surface.
A bearing plate 11 is fixed to the rear surface of the orbiting scroll 7. A tubular boss 15 projects at the center of the rear surface of the bearing plate 11 and rotatably supports an eccentric axial portion 13 of a driving shaft 12 via a roller bearing 14. A pin-cranks-type self-rotation preventing devices 16 is provided at three points on the outer circumference of the orbiting scroll 7 so that the orbiting scroll 7 may eccentrically revolve around the driving shaft 12 in a housing 17.
In the self-rotation preventing device 16, an eccentric shaft 20 of a main shaft 19 rotatably secured to the housing 17 is rotatably secured via a ball bearing 22 in an eccentric boss 21 at three points on the outer circumference of the rear surface of the bearing plate 11.
A cover plate 23 is fixed on the front surface of the stationary scroll 1 with a screw 24. The orbiting scroll 7 is fixed to the bearing plate with a screw 25.
A rear plate 26 of the stationary scroll 1 is fixed to the front surface of the housing 17 with a bolt 27 and a nut 28. Engagement grooves 5a and 9a are formed on the tip ends of the stationary wrap 5 and the orbiting wrap 9 respectively, and sealing members “S” that fit in the engagement grooves 5a and 9a are in sliding contact with the orbiting end plate 8 of the orbiting scroll 7 and the stationary end plate 4 of the stationary scroll 1 respectively.
Long-time use of such a scroll fluid machine causes wear of the sealing member “S” on the tip end of the stationary wrap 5 or orbiting wrap 9 and clearance of the bearings, thereby making contact pressure to the opposite end plate 8 or 4 unsuitable. Unevenness in temperature and pressure of each part makes the stationary end plate 4 or orbiting end plate 8 tilted with respect to the axis of the driving shaft 12 or involved in surging.
Its performance decreases and each part generates heat or noise. So it is necessary to correct engagement degree or clearance between the stationary wrap 5 and the orbiting wrap 6 or inclination with respect to the surface perpendicular to the axis of the driving shaft 12.
To adjust axial clearance between the stationary scroll and the orbiting scroll in the scroll fluid machine or to correct squareness with respect to the driving shaft, there are two methods below:
A) To insert a shim or other suitable spacer into a contact surface between the stationary and orbiting scrolls; and
B) To adjust axial engagement depth of the main shaft of the crankshaft 20 in the self-rotation preventing device with respect to the housing.
According to the method “A”, without special technique, axial clearance can be adjusted easily at low cost. It is necessary to insert a suitable-thickness shim between the stationary and orbiting scrolls and to assemble it after axial clearance is measured in the assembling and disassembled, which is troublesome. It is impossible to make sure of whether the selected shim could have a suitable thickness, without assembling again. A desired axial clearance cannot be obtained by a shim.
The method “B” enables axial clearance to be adjusted while it is measured without disassembling the stationary and orbiting scrolls, but it is necessary to move the self-rotation preventing device itself axially with a special tool. It requires high skill and a lot of works to clamp an outer ring of the bearing with a plurality of bolts to keep good balance.
Furthermore, to return the fitted bearing to an original position, it is necessary to pull out the bearing with a special tool and to pressingly fit it again, which requires power and is troublesome.
The detached bearing is usually deformed to make it impossible to be used again.